A COMPARATIVE STUDY OF TWO 47 Tuc GIANT STARS WITH DIFFERENT s-PROCESS ENRICHMENT

Cordero, María José Aguilar; Hansen, C. J.; Johnson, Christian I.; Pilachowski, Catherine A.

doi:10.1088/2041-8205/808/1/l10

Cited by 10 publications

(10 citation statements)

References 39 publications

(65 reference statements)

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“…Furthermore, 47 Tuc is not among the newly defined class of anomalous GCs, e.g., clusters with clear internal variations in s-process elements and iron. Only one star has been found to be enhanced in the s-process composition, but it is interpreted as due to binarity (Cordero et al 2015).…”

Section: Introductionmentioning

confidence: 96%

Chemical abundances in the multiple sub-giant branch of 47 Tucanae: insights on its faint sub-giant branch component

Marino

Milone

Casagrande

et al. 2016

Mon. Not. R. Astron. Soc.

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The globular cluster 47 Tuc exhibits a complex sub-giant branch (SGB) with a faint-SGB comprising only about the 10% of the cluster mass and a bright-SGB hosting at least two distinct populations. We present a spectroscopic analysis of 62 SGB stars including 21 faint-SGB stars. We thus provide the first chemical analysis of the intriguing faint-SGB population and compare its abundances with those of the dominant populations. We have inferred abundances of Fe, representative light elements C, N, Na, and Al, α elements Mg and Si for individual stars. Oxygen has been obtained by co-adding spectra of stars on different sequences. In addition, we have analysed 12 stars along the two main RGBs of 47 Tuc.Our principal results are: (i) star-to-star variations in C/N/Na among RGB and bright-SGB stars; (ii) substantial N and Na enhancements for the minor population corresponding to the faint-SGB; (iii) no high enrichment in C+N+O for faint-SGB stars. Specifically, the C+N+O of the faint-SGB is a factor of 1.1 higher than the bright-SGB, which, considering random (±1.3) plus systematic errors (±0.3), means that their C+N+O is consistent within observational uncertainties. However, a small C+N+O enrichment for the faint-SGB, similar to what predicted on theoretical ground, cannot be excluded. The N and Na enrichment of the faint-SGB qualitatively agrees with this population possibly being He-enhanced, as suggested by theory. The iron abundance of the bright and faint-SGB is the same to a level of ∼0.10 dex, and no other significant difference for the analysed elements has been detected.

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Section: Introductionmentioning

confidence: 96%

Chemical abundances in the multiple sub-giant branch of 47 Tucanae: insights on its faint sub-giant branch component

Marino

Milone

Casagrande

et al. 2016

Mon. Not. R. Astron. Soc.

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“…A detailed study of slow-neutron capture process (s-process) elements will provide useful information on the formation process of these systems. While there is no abundance measurement of s-process elements for stars in Terzan 5, it is well known that the metal-rich population of peculiar GCs is also enhanced in s-process elements (see, e.g., Marino et al 2011;Cordero et al 2015;Marino et al 2015). Since the s-process enrichment is mainly attributed by AGB stars over a longer period of time (Busso et al 1999;Simmerer et al 2004), this could probe for an age gap between the formation of metalpoor and metal-rich populations.…”

Section: Discussionmentioning

confidence: 99%

Difference in chemical composition between the bright and faint red clump stars in the Milky Way bulge

Lim,

Lee,

Koch

et al. 2020

Preprint

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The double red clump (RC) observed in color-magnitude diagrams of the Milky Way bulge is at the heart of the current debate on the structure and formation origin of the bulge. This feature can be explained by the difference between the two RCs either in distance ("X-shaped scenario") or in chemical composition ("multiplepopulation scenario"). Here we report our high-resolution spectroscopy for the RC and red giant branch stars in a high-latitude field (b ∼ −8.5 • ) of the bulge. We find a difference in [Fe/H] between the stars in the bright and faint RC regimes, in the sense that the bright stars are enhanced in [Fe/H] with respect to the faint stars by 0.149 ± 0.036 dex. The stars on the bright RC are also enhanced in [Na/Fe] but appear to be depleted in [Al/Fe] and [O/Fe], although more observations are required to confirm the significance of these differences. Interestingly, these chemical patterns are similar to those observed among multiple stellar populations in the metal-rich bulge globular cluster Terzan 5. In addition, we find a number of Na-rich stars, which would corroborate the presence of multiple populations in the bulge. Our results support an origin of the double RC from dissolved globular clusters that harbor multiple stellar populations. Thus, our study suggests that a substantial fraction of the outer bulge stars would have originated from the assembly of such stellar systems in the early phase of the Milky Way formation.

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“…Some of the reference GCs in the literature claim to show broad spreads in some abundances past the key CN/CH or Na-O variations. In particular, proton-capture reactions in the progenitors of the second stellar populations tend to produce a mild Mg-Al correlation, while spreads in some s-process elements are also seen, pointing to specific channels of enrichment from asymptotic giant branch (AGB) stars (Marino et al 2015;Cordero et al 2015). Furthermore, Fe spreads have been reported in about ten of the MW GCs studied in detail at high spectral resolutions.…”

Section: Comparison With Outer Halo Gcs Beyond 20 Kpcmentioning

confidence: 95%

Chemical composition of the outer halo globular cluster Palomar 15

Koch

Rich

2019

A&A

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Globular clusters (GCs) in the outer Milky Way halo are important tracers of the assembly history of our Galaxy. Only a few of these objects show spreads in heavier elements beyond the canonical light-element variations that have essentially been found throughout the entire Galactic GC system, suggesting a more complex origin and evolution of these objects. Here, we present the first abundance analysis of three red giants in the remote (R GC = 38 kpc) outer halo GC Palomar 15, based on medium-resolution spectra obtained with the Keck/ESI instrument. Our results ascertain a low iron abundance of −1.94±0.06 dex with no evidence of any significant abundance spreads, although this is based on low number statistics. Overall, abundance ratios of 16 species were measured, including carbon, Na, Al, α-peak (Mg,Si,Ca,Ti) and Fe-peak (Sc,V,Cr,Fe,Co,Ni) elements, and the three neutron-capture elements Sr, Ba, and Eu. The majority of abundances are compatible with those of halo field stars and those found in other GCs in the outer and inner halos at similar metallicity. Pal 15 is enhanced to [Mg/Fe]=0.45 dex, while other α-elements, Ca and Ti, are lower by 0.3 dex. Taking Mg as a representative for [α/Fe], and coupled with the lack of any significant spread in any of the studied elements we conclude that Pal 15 is typical of the outer halo, as is bolstered by its chemical similarity to the benchmark outer halo cluster NGC 7492. One star shows evidence of elevated Na and Al abundances, hinting at the presence of multiple stellar populations in this cluster.

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A COMPARATIVE STUDY OF TWO 47 Tuc GIANT STARS WITH DIFFERENT s-PROCESS ENRICHMENT

Cited by 10 publications

References 39 publications

Chemical abundances in the multiple sub-giant branch of 47 Tucanae: insights on its faint sub-giant branch component

Chemical abundances in the multiple sub-giant branch of 47 Tucanae: insights on its faint sub-giant branch component

Difference in chemical composition between the bright and faint red clump stars in the Milky Way bulge

Chemical composition of the outer halo globular cluster Palomar 15

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